There is a case such that in order to reduce a noise which is generated in accordance with switching operation of a semiconductor module, in the immediate vicinity of a semiconductor module, a junction between a terminal of a semiconductor module and a base conductor which functions also as a heat radiator is connected by a noise reduction capacitor. Especially, in a case where a SiC element is used as a semiconductor element, generally, a noise which is generated by a semiconductor module is increased, therefore, necessity of reducing a noise in the immediate vicinity of a semiconductor is increased so as not to conduct a noise to outside the semiconductor module.
Patent Document 1 discloses such that a noise can be reduced by mounting a filter capacitor in a semiconductor module so as to connect with a base which functions also as a heat sink Patent Document 2 discloses such that a ground conductor on which a semiconductor module is mounted is extended, a first insulator is sandwiched between a positive pole conductor and a ground conductor, a second insulator is sandwiched between a negative pole conductor and a ground conductor so as to form a Y capacitor, as a result, a noise can be reduced.
Further, there is a case such that in order to suppress increase of a temperature of a smoothing capacitor which is connected to a semiconductor module due to heating of a semiconductor module, a semiconductor module terminal is thermally contacted with a heat radiator. Generally, modules are thermally designed on conditions such that heat resistance temperature of a Si element does not exceed approximately 150 degrees Celsius, however in a case where a SiC element is used as a semiconductor element, in some cases, a semiconductor module is thermally designed on conditions such that a semiconductor module becomes a temperature higher than 200 degrees Celsius. A temperature of a smoothing capacitor is approximately 125 degrees Celsius at highest, even when a thermal design of a semiconductor module is achieved, heat is conducted from a semiconductor module to a smoothing capacitor, and there is a problem such that a temperature of a smoothing capacitor exceeds an upper limit temperature. Therefore, necessity to sufficiently cool a joint between a semiconductor module and a smoothing capacitor is increased. Patent Document 3 discloses such that via an insulator, by fixing a junction between a semiconductor module terminal and a smoothing capacitor terminal to a cooling device, temperature increase of a smoothing capacitor can be suppressed.